This invention relates to a temperature controller which can accurately compensate for cold junction temperature of a thermocouple.
In a temperature controller body connected, by of plugs, to a plurality of connection terminals for external wiring, there is provided a hollow raised portion for positioning a pin pattern constituting the plugs to the socket. The raised portion houses therein a resistor for compensating for the cold junction of the thermocouple. The socket and recessed portion are formed with holes for maintaining the resistor at a temperature equal to that of open air. In the internal circuit, the cold junction temperature of the thermocouple connected to the connection terminals is compensated for in accordance with the detected value of the resistor, and the thus compensated temperature is represented by the true temperature of an article to be measured.
However, in practice, the ambient temperature of the resistor is sometime different from temperatures of the thermocouple connecting the external terminals or the ambient temperature thereof.
For example, where the length of the thermocouple or compensation conductor is short, a great difference between the temperature of the cold junction connecting terminal and the ambient temperature of the resistor sometimes occurs as a result of the terminal transmission from the temperature measuring portion or the like. Therefore, a great difference between the true temperature and detected temperature of an article to be measured occurs, disadvantageously failing to achieve the accurate temperature display or the proper temperature control on the basis thereof.